Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Log each test case status in a task"
  - Log each test case status in a task

    JIRA: YARDSTICK-785

    Currently if one test case failed, we will log error.
    But if one case success, we do not have any tips.
    We need log success when one case success.

    Change-Id: I0f41ac55f2569f44b787133e3f2594a5c5547f4a
    Signed-off-by: chenjiankun <chenjiankun1@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 199e183..b255257 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 199e183885901f9cd95d489ec7b9b40aa481b724
+Subproject commit b2552579f300ec9f4c2b516eb44cac0efb3d4dd6